Yu's appointment underscores social network's emergence as a major player in the Web industry. In many ways, Facebook has
expanded the scope of social networking by encouraging software developers to use it as a platform for the Internet's hottest trend: consumers' use of mini Web applications known as "widgets."
Effectively, widgets act like mini Web browsers, allowing consumers to post dynamic or interactive content to their Web pages. Experts say Facebook is turning the Web into a software operating system for distributing programs to consumers. According to investor Peter Thiel, the company is now worth between $7 billion and $10 billion and could be exploring a possible sale or an IPO. Last year, Yahoo sought to buy the company for $1 billion.